1-Oxa-2,6-disilacyclohexane-4-carboxamides

ABSTRACT

Silicon-containing amides, e.g., N-[1&#39;-phenyl-2&#39;-(4&#34;-methylphenyl)ethyl]-2,2,6,6-tetramethyl-1-oxa-2,6-disilacyclohexane-4-carboxamide, are useful as anti-atherosclerotic agents. The amides are obtainable by acylation of a primary amine (the substituents on the amine being of the aralkyl phenyl, tryptophanyl, benzocycloalkyl-type) with a corresponding silicon-containing carboxylic acid (or active form thereof).

This invention relates to organic compounds and more particularly to silicon-containing fatty acid amides and to pharmaceutical compositions containing such compounds, as well as to the pharmaceutical use of such compounds.

The compounds of this invention are conveniently represented by the formula I: ##STR1## wherein each of R¹, R², R³ and R⁴ is, independently, lower alkyl having from 1 to 4 carbon atoms, e.g., methyl, and R is of type (a) an aralkyl-type radical of the structure: ##STR2## wherein g is 0, 1 or 2;

R^(a) is a hydrogen atom, halo having an atomic weight of from about 19 to 127, alkoxy having from 1 to 4 carbon atoms, or alkyl having from 1 to 4 carbon atoms, or trifluoromethyl;

R^(b) is a hydrogen atom, alkyl having from 1 to 3 carbon atoms, alkoxy having from 1 to 3 carbon atoms, or halo having an atomic weight of from about 19 to 36; and

R^(c) is subtype (i) a hydrogen atom; subtype (ii) a radical of the structure ##STR3## in which p is 0, 1 or 2, and

y is a hydrogen atom, halo having an atomic weight of from about 19 to 127, alkoxy having from 1 to 4 carbon atoms, or alkyl having from 1 to 4 carbon atoms; and

y' is a hydrogen atom, alkoxy having from 1 to 3 carbon atoms, alkyl having from 1 to 3 carbon atoms, or halo having an atomic weight of from about 19 to 36; or subtype (iii) alkyl having from 1 to 8 carbon atoms; or R is of type (b) a phenyl-type radical of the structure ##STR4## in which R^(b) is as defined above, and

R^(o) is a hydrogen atom, halo having an atomic weight of from about 19 to 127, alkoxy having from 1 to 4 carbon atoms, or alkyl having from 1 to 4 carbon atoms; or

R^(o) is a radical of the structure R^(f) : ##STR5## in which D is --CH₂ -- or --O--;

f is 0 or 1; and

W is a hydrogen atom, halo having an atomic weight of from about 19 to 80, alkoxy having from 1 to 3 carbon atoms, or alkyl having from 1 to 3 carbon atoms; or

R is of type (c) an indolyl radical of the structure: ##STR6## wherein R^(b) is as defined above;

R⁶ is alkyl having from 1 to 8 carbon atoms or benzyl; and

R⁷ is a hydrogen atom, alkyl having from 1 to 8 carbon atoms or benzyl; or

R is (d) a benzocycloalkyl nucleus of the structure: ##STR7## wherein y and y' are as defined above; and

j is a whole integer of from 1 to 4.

It is preferred that R¹ and R³ are unbranched. It is further preferred that none of R¹ to R⁴ is a branched alkyl. Preferably each of R¹ to R⁴ is the same radical, especially methyl.

Further preferred forms of Compounds I when R is of type (a) or (b) and R^(o) is not R^(f), are that it is preferred that when R^(a), R^(o) or y is other than a hydrogen atom and R^(b) (or y') is a hydrogen atom, that R^(o), or R^(a), or y be located at the 4-position; and that when R^(b) (or y') is also other than a hydrogen atom that R^(a) and R^(o) and R^(b) (or y and y') are the same, and it is additionally preferred that they be located at the 2- and 4-positions of the phenyl ring. When R is of type (a) where g=1, and R^(c) is of type (ii) where p=0, then R can be an α-(phenyl)-β-(p-methylphenyl)ethyl radical, and when R^(c) is of type (ii) where p=1, then R can be an α-(benzyl)-phenylethyl radical, these radicals being also known as 1'-phenyl-2'-(p-methylphenyl)ethyl and 1'-benzyl-2'-phenylethyl, respectively.

With particular respect to the substituent R^(o) when it is a radical R^(f), it will be appreciated that when D=CH₂ and f=1, then the radical R^(f) is of the benzyl type. When D=oxygen and f=1, then the radical R^(f) is of the phenoxy-type. When f=zero, then the radical R^(f) is of the phenyl-type. Hence, when R is of type (b), and R^(o) is of type R^(f) where f=zero, then R can be a biphenylyl radical. The radical R^(f) is preferably at the para-position. When W is other than a hydrogen atom, it is preferably at the para-position.

With respect to R, when it is of type (c), it is preferred that when R^(b) is other than a hydrogen atom, it be located at the 5-position of the indole nucleus. It is also preferred that when R⁶ is alkyl, it is unbranched, particularly ethyl.

With respect to R when it is of type (d) it is preferred that when y is other than a hydrogen atom, that it be located at a carbon atom ortho to the ring junction; and that when y' is also other than a hydrogen, it is preferred that it be the same as y, and it is additionally preferred that it be in para-relationship to y'. It is additionally preferred that the amide group be linked to a carbon of the cycloalkyl moiety which is directly bonded to a ring junction carbon. It is also preferred that j be 1, i.e. that the benzocycloalkyl nucleus be indanyl, and particularly 1-indanyl.

In the above-presented definitions, where R^(o), R^(a) or y is halo, it is preferably fluoro or chloro, and particularly chloro; and when R^(b) or y' is halo it is preferably chloro.

Compounds I of this invention may be obtained by reaction of a primary amine (II) bearing the desired moiety-R as defined above with a compound III, i.e. a carboxylic acid (or derivative thereof) bearing the "acyl" portion of the desired Compound I. Such acylation may be carried out by conventional means employed in converting a primary amine function to its corresponding secondary amide, such as are reported in the literature.

The compounds of formula (I) may be prepared according to the following reaction scheme (process a): ##STR8## wherein R is as defined above; A is the radical: ##STR9## in which R¹, R², R³ and R⁴ use as defined above, and X is hydroxy, alkoxy or aryloxy, or halo having an atomic weight of from about 35 to 80, i.e. chloro or bromo, a pseudo-halide, or III may be an "anhydride" or a "mixed anhydride", or the like as are well known in the art.

A particularly convenient method of preparing compounds I comprises reacting (process a1) an acyl halide of the formula IV: ##STR10## in which A is as defined above, and X' is either chloro or bromo, with a compound II (as defined above), in the presence of an acid acceptor e.g. an organic base, such as triethylamine or excess of compound II, in an inert medium at moderate temperatures, e.g. from about -50° to +50° C. preferably at about 0° to +30° C., in an inert medium e.g. a chlorinated hydrocarbon, such as dichloromethane, or an aromatic hydrocarbon, such as toluene.

The acyl halides (IV) may be prepared in the conventional manner, e.g. by treating (process b1) a corresponding compound III (as defined above), in which X is OH, i.e. a compound V, with a halogenating agent capable of contributing a chlorine or bromine atom, e.g. oxalyl chloride or thionyl chloride (or -bromide, as appropriate).

Similarly, the acylation (process a) may conveniently be carried out by a mixed anhydride technique (process a2) wherein a compound II is treated with a mixed anhydride of the formula III': ##STR11## in which A is as defined above and R⁸ is a lower alkyl having from 1 to 6 carbon atoms, at moderate temperatures, e.g. from about -10° C. to +35° C., in an inert organic medium, e.g. a chlorinated hydrocarbon, such as methylene chloride.

The mixed anhydrides (III') are obtainable by reacting (process b2) a free carboxylic acid of the formula V: ##STR12## wherein A is as defined above, with a chloroformate of the formula VI: ##STR13## wherein R⁸ is as defined above, in the presence of an acid acceptor, e.g. an organic base, such as triethylamine, at reduced temperatures, e.g. at from about -10° to +30° C., in an inert organic medium, e.g. a chlorinated hydrocarbon, such as methylene chloride.

In the above-described processes, neither the media nor the temperature are critical to the reactions, and where the reactants or reagents are liquid, an excess thereof may serve as the reaction medium. If desired a compound II may be in the form of an acid addition salt, for example the hydrochloride. The mixed anhydride (III') resulting from (process b2) may be conveniently be used in situ. That is to say that provided that the materials in the reaction mixture containing the mixed anhydride are not detrimental, they may be used directly for (process a2) without recovery.

Reagents and reactants described herein, e.g., compounds II, III, III', IV, V, and VI are known and obtainable by known means, or where not known, may be obtained by adaptation of methods reported in the literature for the preparation of known analogs; many such compounds being commercially available. For example, a compound V in which each of R¹, R², R³ and R⁴ is methyl is disclosed in Chem. Berichte 97, 1047 (1947).

The final products and intermediate compounds described herein may be recovered and refined, where such is desired, by conventional means, such as by crystallization, distillation or chromatographic techniques such as column or thin layer chromatography.

STATEMENT OF UTILITY

The compounds of formula I of this invention are useful as pharmaceutical agents in animals. In particular, the compounds of the formula I are useful as anti-atherosclerotic agents, i.e. agents useful in the prophylactic treatment of atherosclerosis and in the controlling of atherosclerotic conditions due to cholesterol ester accumulation in the arterial walls. Such ability of the compounds of the formula I is indicated e.g., by known test procedures in which the total cholesterol ester content of cultured cells is shown to be reduced by a test compound, as compared to untreated cells, and carried out, for example, by the following procedures:

(A) Cell Culture

Fu5AH rat hepatoma cells (Rothblat, G.M., Lipids 9, 526-535; 1974) are routinely grown in 75 cm² tissue culture flasks using Minimum Essential Medium (Eagle) supplemented with 10% fetal bovine serum. For testing a 75 cm² flask with a near confluent cell growth is selected. The cells are removed from the flask surface by mild enzymatic treatment with pronase. After centrifugation and decanting the enzyme solution, the cell pellet is resuspended in an appropriate volume of media for seeding the desired number of 60 mm tissue culture dishes. Five (5) ml of the diluted cell suspension are pipetted into each dish. After seeding, the dishes are labelled with the cell type, date and flask number of origin and incubated at 37° C. in approximately 5% CO₂ atmosphere in a high humidity incubator. When the cultures are confluent, the actual drug testing is begun. Test compounds are routinely solubilized in 100% ethanol. An equivalent amount of ethanol is added to control groups as well. The tissue culture dishes are randomly divided into groups. To one group, hyperlipemic rabbit serum (HRS) is added at 5% by volume (control). To the remaining groups, 5% HRS and 0.1 mg to 1 mg per 100 ml of media of the test compound are added. The dishes are returned to the incubator for an additional 24 hours. All operations through to the final incubation are performed using sterile technique in a laminar flow hood. After the incubation period, the dishes are microscopically observed with the Zeiss Axiomat with phase contrast optics and the conditions of the cultures are recorded; especially in regard to the shape, size, number and configuration of cytoplasmic lipid inclusions. A qualitative assessment of inclusions in test compound-treated group relative to control and standard is made, re,

(1) no drug effect;

(2) reduced number of inclusions

<,=,> standard.

The standard is α-(1-oxo-9-octadecenylamino)-1H-indole-3-propionic acid, ethyl ester (cis isomer)*, preparation of which is disclosed in Belgian Patent 873,365 (Derwent 50,8858) and British Patent No. 2,012,261A. Alternatively, may be used (±) 4,4-dimethyl 4-sila-tetradecanoyl-1'-phenyl-2'-p-tolyl-ethylamide reported in the literature, e.g., European Patent No. 12,183**. A reduction in the number and size etc. of the inclusions indicates a reduction in cholesterol ester accumulation.

The antiatherosclerotic effective dosage of active ingredient employed for the reduction of cholesterol ester content in the arterial walls of a mammal may vary depending on the particular compound employed, the mode of administration and the severity of the condition being treated. However, in general, satisfactory results are obtained when the compounds of formula I are administered at a daily dosage of from about 0.2 milligrams to about 500 milligrams per kilogram of animal body weight, preferably given in divided doses two to four times a day, or in sustained release form. For most large mammals, the total daily dosage is from about 500 mg. to 15,000 mg., preferably from about 1000 mg. to 5,000 mg. Dosage forms suitable for internal use comprise from about 250 mg. to 7,500 mg e.g., from about 250 mg. to 2,500 mg. of the active compound in intimate admixture with a solid or liquid pharmaceutically acceptable carrier. Solid carriers include starch, lactose and kaolin, while liquid carriers include sterile water, polyethylene glycols and edible oils such as corn, peanut and sesame oils, as are appropriate to the nature of the active ingredient and the particular form of administration desired. Adjuvants customarily employed in the preparation of pharmaceutical compositions may be advantageously included, such as flavoring agents, coloring agents, preserving agents, and antioxidants e.g. vitamin E, ascorbic acid, BHT and BHA.

The compounds are preferably administered orally. The preferred pharmaceutical compositions from the standpoint of ease of preparation and administration are solid compositions for oral administration, particularly tablets and hard-filled or liquid-filled capsules.

Where the final product (I) is waxy or oily and oral dosages in the higher ranges are desired, the product may conveniently be administered in an aqueous suspension; the flavor thereof being enhanced by fruit flavors and the like, e.g., as a "milk shake" or "cocktail", by methods well known in the art, e.g., using CMC as a suspending agent.

When the compounds I are employed for the above utility, they may be combined with one or more pharmaceutically acceptable carriers, e.g., solvents, diluents and the like, and may be administered orally in such forms as tablets, capsules, dispersible powders, granules, suspensions containing, for example, from about 0.5 to 5% of suspending agent, syrups containing, for example, from about 10 to 50% of sugar, and elixirs containing, for example, from about 20 to 50% ethanol, and the like, or parenterally in the form of sterile injectable solutions or suspensions containing from about 0.5 to 5% suspending agent in an isotonic medium. These pharmaceutical preparations may contain, for example, from about 0.5% up to about 90% of the active ingredient in combination with the carrier, more usually between 5% and 60% by weight.

Representative formulations for administration orally three times a day prior to feeding in the treatment of atherosclerosis is a gelatin capsule prepared by conventional techniques to contain the following

    ______________________________________                                         Ingredient            Weight (in Mg.)                                          ______________________________________                                         1'-phenyl-2'-(4"-methyl phenyl)-                                                                     300     500                                              ethyl-2,2,6,6-tetramethyl-1-oxa-                                               2,6-disilacyclohexane-4-carboxamide                                            Lactose               200     --                                               ______________________________________                                    

While the inventor does not wish to be bound by any proposed theory of the mechanism of the action of Compounds I, it has been observed in tests on analogous compounds using the Zilbersmit Dual Isotope Method* that such compounds substantially reduce absorption of cholesterol from the gastro-intestinal system of the host, i.e. at the intestinal wall, possibly by action involving the Acyl Coenzyme A cholesterol acyl transferase (ACAT) enzyme, resulting in a marked reduction of cholesterol intake into the blood of the host, as well as a reduction in the cholesterol content (in free and as ester form) of smooth muscle cells of the host, e.g. arterial walls, such as those of the aorta and coronary arteries, thus minimizing or avoiding plaque formation therein.

Employing the above-described cell culture test method (using Fu5AH cells) and as test compound* the product of Example 1, below, marked activity is observed at the 1 mq. level.

The following examples of the preparation of intermediates and final compounds (I) of the invention are illustrative of the invention. All temperatures are centigrade (°C.) and room temperature is 20° to 30° C., unless indicated otherwise.

It will be appreciated that the products of these examples may exist in the form of stereoisomers, e.g. optically active isomers, although, e.g. (±) racemic mixtures or a particular form are specifically mentioned.

EXAMPLE 1 N-[1'-phenyl-2'-(4"-methylphenyl)ethyl]-2,2,6,6-tetramethyl-1-oxa-2,6-disilacyclohexane-4-carboxamide ##STR14## Step A 2,2,6,6-tetramethyl-1-oxa-2,6-disilacyclohexane-4-carboxychloride (a compound IV) ##STR15##

4.13 g (18.9 mmol) of 2,2,6,6-tetramethyl-1-oxa-2,6-disilacyclohexane-4-oic acid is dissolved in 40 ml of dry dichloromethane and 20 ml of dry toluene containing 0.05 ml of N,N-dimethylformamide. To this solution, 1.9 ml (26.4 mmol) of thionyl chloride is added with stirring in an ice bath. Stirring is continued at 25° for 2 hours, after which the solution is concentrated to an oil (the acid chloride product), which is retained under anhydrous conditions and used in Step C, below, as soon as possible (chilled to -20° if not used promptly).

Step B 1-phenyl-2-(4'-(methylphenyl)ethyl amine, (a compound II)

The free amine is prepared by shaking 5.2 g (21.0 mmol) of 1-phenyl-2-(p-tolylethyl)amine hydrochloride* with excess NaOH solution and dichloromethane as solvent. The organic layer is diluted with toluene, dried over anh. sodium sulfate and concentrated to about 5.4 g oil, (a small residue of toluene remaining is not detrimental). The thus-freed amine, is promptly used in Step C, below.

Step C N-(1'-phenyl-2'-(4"-methylphenyl)ethyl-2,2,6,6-tetramethyl-1-oxa-2,6-disilacyclohexane-4-carboxamide

The acyl chloride product (oil) obtained in Step A is dissolved in 30 ml of dry dichloromethane and the solution added to a solution of the free amine (obtained in Step B) in 2.8 ml (20 mmol) of triethylamine and 30 ml of dry dichloromethane, while stirring in an ice bath.

The reaction mixture is further stirred at 25° for 1 hr., then extracted with cold 10% aqueous sodium hydroxide, dried over anh. sodium sulfate and concentrated to 9.6 g of crude product. The latter, in ethyl acetate solution, is extracted with dilute hydrochloric acid then with brine containing NaHCO₃, dried over anh. sodium sulfate and recovered by concentration. Recrystallization from toluene and vacuum drying at 100° for 1 hr. yields 4.8 g of microanalytically pure title product, mp (148)-150°-151°.

EXAMPLE 2 N-(1'-benzyl-2'-phenyl)-ethyl-2,2,6,6-tetramethyl-1-oxa-2,6-disilacyclohexane-4-carboxamide. ##STR16##

Repeating the procedure of Example 1, but in place of the 1-phenyl-2-(4-methylphenyl)amine used therein, using an approximately equivalent amount of 2-benzyl-1-phenylethylamine, there is accordingly obtained the title product of this example, mp 142° C.

EXAMPLE 3

Repeating the procedure of Example 1, but using in place of the 1-phenyl-2-(p-methylphenyl)ethylamine used therein, an approximately equivalent amount of the following amines as compounds II:

(a) 1-amino-indane;

(b) DL-tryptophan ethyl ester, hydrochloride;*

(c) (d,l) α-methylbenzylamine;

(d) 2-methylaniline; or

(e) 1-[p-methylbenzyl-2'-(p-methylphenyl)ethyl]amine,

there is accordingly obtained, respectively (Compounds I):

(a) N-indanyl-2,2,6,6-tetramethyl-1-oxa-2,6-disilacyclohexane-4-carboxamide;

(b) N-[(O-ethyl)-DL-tryptophanyl]-2,2,6,6 tetramethyl-1-oxa-2,6-disilacyclohexane-4-carboxamide;

(c) N-(d,l-α-methylbenzyl)-2,2,6,6-tetramethyl-1-oxa-2,6-disilacyclohexane-4-carboxamide;

(d) N-(2-methylphenyl)-2,2,6,6-tetramethyl-1-oxa-2,6-disilacyclohexane-4-carboxamide;

(e) N-[1'-(p-methylbenzyl)-2'(p-methylphenyl)ethyl]-2,2,6,6-tetramethyl-1-oxa-2,6-disilacyclohexane-4-carboxamide;

EXAMPLE 4

Repeating the procedure of Examples 1, 2 and 3 but using in place of the 2,2,6,6-tetramethyl-1-oxa-4-carboxy-2,6-disilacyclohexane used therein, in approximately equivalent amount of 2,2,6,6-tetraethyl-1-oxa-4-carboxy-2,6-disilacyclohexane, there are accordingly obtained the corresponding amides in which R¹, R², R³ and R⁴ are ethyl, rather than methyl. 

What is claimed is:
 1. A compound of the formula: ##STR17## wherein each of R¹, R², R³ and R⁴ is, independently, alkyl having from 1 to 4 carbon atoms; andR is of type (a) an aralkyl-type radical of the structure ##STR18## wherein g is 0, 1 or 2; R^(a) is a hydrogen atom, halo having an atomic weight of from about 19 to 127, alkoxy having from 1 to 4 carbon atoms, or alkyl having from 1 to 4 carbon atoms, or trifluoromethyl; R^(b) is a hydrogen atom, alkyl having from 1 to 3 carbon atoms, alkoxy having from 1 to 3 carbon atoms, or halo having an atomic weight of from about 19 to 36; and R^(c) is subtype (i) a hydrogen atom; subtype (ii) a radical of the structure ##STR19## in which p is 0, 1 or 2, and y is a hydrogen atom, halo having an atomic weight of from about 19 to 127, alkoxy having from 1 to 4 carbon atoms, or alkyl having from 1 to 4 carbon atoms; and y' is a hydrogen atom, alkoxy having from 1 to 3 carbon atoms, alkyl having from 1 to 3 carbon atoms, or halo having an atomic weight of from about 19 to 36; or subtype (iii) alkyl having from 1 to 8 carbon atoms; or R is of type (b) a phenyl-type radical of the structure ##STR20## in which R^(b) is as defined above, and R^(o) is a hydrogen atom, halo having an atomic weight of from about 19 to 127, alkoxy having from 1 to 4 carbon atoms, or alkyl having from 1 to 4 carbon atoms; or R^(o) is a radical of the structure R^(f) : ##STR21## in which D is --CH₂ -- or --O--; f is 0 or 1; and W is a hydrogen atom, halo having an atomic weight of from about 19 to 80, alkoxy having from 1 to 3 carbon atoms, or alkyl having from 1 to 3 carbon atoms; or R is of type (c) an indolyl radical of the structure: ##STR22## wherein R^(b) is as defined above; R⁶ is alkyl having from 1 to 8 carbon atoms or benzyl; and R⁷ is a hydrogen atom, alkyl having from 1 to 8 carbon atoms or benzyl; or R is (d) a benzocycloalkyl nucleus of the structure: ##STR23## wherein y and y' are as defined above; and j is a whole integer of from 1 to
 4. 2. A compound of claim 1 in which R is of type (a).
 3. A compound of claim 1 in which R is of type (b).
 4. A compound of claim 1 in which R is of type (c).
 5. A compound of claim 1 in which R is of type (d).
 6. A compound of claim 6 in which each of R¹, R², R³ and R⁴ are the same.
 7. A compound of claim 6 in which each of R¹, R², R³ and R⁴ is methyl.
 8. The compound of claim 1 in which R is 1'-phenyl-2'-(4-methylphenyl)ethyl.
 9. The compound of claim 1 which is N-(1'-benzyl-2'-phenyl)ethyl-2,2,6,6-tetramethyl-1-oxa-2,6-disilacyclohexane-4-carboxamide.
 10. The compound of claim 1 which is N-[1'-phenyl-2'-(4"-methylphenyl)ethyl]-2,2,6,6-tetramethyl-1-oxa-2,6-disilacyclohexane-4-carboxamide.
 11. A method of inhibiting the accumulation of cholesterol ester in an arterial wall of a mammal in need of such treatment, comprising administering a cholesterol ester-inhibiting amount of a compound of claim 1 to said mammal.
 12. A pharmaceutical composition suitable for inhibiting the accumulation of cholesterol ester in arterial wall of a mammal comprising a cholesterol ester-inhibiting-effective amount of a compound of claim 1 and a non-toxic pharmaceutically-acceptable carrier.
 13. A composition of claim 12 in solid form.
 14. A composition of claim 12, in which the compound is present in an amount of from about 250 to 7,500 milligrams.
 15. A method of claim 11 in which the daily dose of the compound is from about 500 mg to 15,000 mg. 